The present invention relates to an arrangement for the removal of soot particles from the exhaust gas stream of a diesel internal combustion engine with a soot particle collecting section arranged in the exhaust gas line, in which conductor elements are arranged that are at a different potential for catching the soot particles.
In an arrangement of the aforementioned type, disclosed in the Japanese Patent No. 57-16311, the soot particle collecting section consists of a combination of several conductor plates disposed at different potential between which is provided a granulate for catching the soot particles. However, as the soot particle collecting section must extend over the entire cross section of the exhaust gas flow, it represents a relatively large flow resistance that causes a high exhaust gas counterpressure.
Furthermore, it is known from the EP-A No. 15 26 23 to catch the soot particles of an exhaust gas stream in a soot particle chamber connected to a centrifugal separator and to conduct the purified exhaust gas stream into the atmosphere on the opposite side.
The present invention is concerned with the task to provide an arrangement of the type described above, by means of which a soot particle removal from the exhaust gas stream is realizable in a simple manner and without significant increase of the exhaust gas counterpressure.
The underlying problems are solved according to the present invention in that a centrifugal separator is connected to the exhaust gas line, in that the soot particle collecting section is a soot particle collecting chamber disposed on the downstream side of the centrifugal separator connected with the same and constructed axially symmetrical with respect to the longitudinal axis thereof, in that a predetermined number of electrodes is arranged at a slight distance from the casing interior surface of the soot particle collecting chamber and in that the electrodes are at a different potential among one another or the electrodes and soot particle collecting chamber itself are at a different potential. In the alternative, the underlying problems are solved according to the present invention in that a device for the ionization of soot particles that flow past the same, is provided in the exhaust gas line upstream of the soot particle collecting section, in that an electrostatically charged first electrode is arranged in the soot particle collecting section within the area of the longitudinal center axis thereof, in that the first electrode is surrounded by an oppositely electrically charged counter-electrode that is arranged in direct proximity of the wall of the exhaust gas line, in that a burning-off electrode permeable to soot particles is placed at a small distance in front of the first electrode or the counter-electrode, in that a low voltage is applied between the electrode which has the burning-off electrode placed in front of it, and the burning-off electrode itself, and in that the ionized soot particles and the electrode which has the burning-off electrode placed in front of it, possess an opposite charge.
It is assured with the arrangements according to the present invention that a maximum proportion in soot particles is burned off in a simple manner by short-circuiting two electrical conductors while at the same time a significant impairment of the exhaust gas flow carrying along the soot particles does not exist. According to another feature of the present invention, the electrodes are arranged over the circumference of a soot particle collecting chamber connected to a centrifugal separator of known type (cyclone separator) and thus form no flow obstacle disposed directly in the exhaust gas flow.
If, according to still another feature of the present invention, the electrodes are bent angularly toward the interior of the soot particle collecting chamber on their side facing the flow of the soot particles, one obtains additionally the advantage that soot particles are also collected which move on a circular path somewhat further away from the casing interior surface of the soot particle collecting chamber.
According to a further feature of the present invention, a predetermined number of electrodes inclined toward the interior of the soot particle collecting chamber is arranged distributed over the interior circumference of the soot particle collecting chamber whereby the spacing of the electrodes with respect to the casing interior surface of the soot particle collecting chamber is greater on their side facing the flow of the soot particles than on the opposite side. This arrangement of the electrodes enables a burning off of a greater number of previously collected soot particles.
Even though according to another embodiment of the present invention the individual electrodes are located in the exhaust gas stream, the end face of the electrodes which effectively face the flow of the exhaust gases is very small in comparison to the overall exhaust gas line cross section. In order that the individual soot particles are nonetheless conducted between the electrodes causing their burning-off, a correspondingly built up electric field is provided which deflects the previously ionized soot particles in the direction of the electrodes partaking in the burning off of the soot particles.
Even if as a result of a trouble in the current supply of the burning-off electrodes, a burning off of the soot particles is prevented, the exhaust gases together with soot particles can still flow off into the atmosphere without having to overcome greater flow resistances. A closing of the exhaust gas line by a clogging-up exhaust gas line and therewith necessarily a stoppage of the internal combustion engine as a result of an excessively high exhaust gas counterpressure is therewith precluded in accordance with the present invention.